VP9 is the successor to VP8 and competes mainly with MPEG's High Efficiency Video Coding (HEVC/H.265). At first, VP9 was mainly used on Google's video platform YouTube. The emergence of the Alliance for Open Media, and its support for the ongoing development of the successor AV1, of which Google is a part, led to growing interest in the format.
In contrast to HEVC, VP9 support is common among modern web browsers (see HTML5 video § Browser support). Android has supported VP9 since version 4.4 KitKat, while iOS/iPadOS added support for VP9 in iOS/iPadOS 14
Parts of the format are covered by patents held by Google. The company grants free usage of its own related patents based on reciprocity, i.e. as long as the user does not engage in patent litigations.